1. Field of the Invention
The present invention relates to a three-dimensional modeling technique for producing three-dimensional shape data of a target from a plurality of image data of the target, and in particular to three-dimensional modeling apparatus, method, and medium, and three-dimensional shape data recording apparatus, method, and medium.
2. Description of the Related Art
Conventionally, it is widely known to use a silhouette method where three-dimensional shape is estimated from silhouette information of a target, a triangulation method using a laser light, or a space coding method where a plurality of black-and-white patterns are projected, as a method for producing various three-dimensional images.
In the silhouette method, the shape data is produced as follows. For example, the target is placed on a rotational table, a plurality of images are captured with a suitable angle difference, and a silhouette image of the target is determined for each of the images. Here, by using a background plate such as a blue background during the capturing process, silhouette images can be easily and stably obtained using a widely-known chroma key technique.
If the positional relationship between the rotational table and the capturing camera is accurately known in advance, a silhouette can be projected to the assumed three-dimensional space on the rotational table from each viewpoint. The space where all silhouettes are projected is extracted as the object region. In this manner, the three-dimensional shape of the target is estimated.
The triangulation method using a laser light, on the other hand, uses a laser light irradiating device having a basic structure as shown in FIG. 15. Specifically, as shown in FIG. 15, a beam shape laser light is converted to a slit light by a cylindrical lens and the direction of the slit light is altered using a galvano-mirror or a polygon mirror, to allow a two-dimensional scan.
The laser light irradiated onto the target in this manner is then captured by an image inputting section such as a camera. The laser light has a sufficiently larger intensity than a typical illumination light, and thus, the point (or line) of maximum luminance can be easily extracted from the input image. The positional relationship between the laser light source and the image inputting section is accurately measured in advance. If the angle of the mirror when the image is input is accurately known, the distance from the camera or the laser light source to the target can be calculated using the principle of triangulation.
In a space coding method, a plurality of black-and-white patterns such as the patterns shown in FIG. 9 are projected onto a target and the target is captured. Then, for each image, it is determined which of the black or white pattern is projected on each pixel. It is known that the accuracy can be improved by comparing the projected image with an image projected by a pattern obtained by inverting the patterns described above.
In this manner, when seven patterns are projected, for example, the image can be divided into a total of 128 strip regions. If the direction of the pattern and the direction of the camera towards the irradiating section are approximately perpendicular, the pattern sequence of each pixel and the direction of the light from the pattern projecting section can be associated. Thus, the distance between the camera or the laser light source to the target can be calculated based on the principle of triangulation.
In the above silhouette method, the three-dimensional shape can be estimated once the background and the target are separated and silhouette information is obtained. Thus, there is no limitation on the material or the color of the target. However, there is a problem that the three-dimensional shape of any shape that does not show a silhouette outline cannot be accurately estimated. Specific examples of such a shape include the internal section of a cup. This portion always corresponds to the internal silhouette of another portion and cannot be observed as a silhouette outline, and the three-dimensional shape cannot be accurately estimated by the silhouette method.
In the triangulation method using a laser light and space coding method, on the other hand, it is fundamentally necessary to irradiate light onto the target and distinguish between the irradiated and non-irradiated sections. However, in a black portion, for example, the hair portion of a person, this distinction is very difficult. Therefore, in the triangulation method using laser light and space coding method, it is difficult to obtain the three-dimensional shape information for materials and colors that absorb light. There is a solution to this problem using a very strong laser light, but when the target is a person, there will be a problem regarding safety.
In addition, because a plurality of patterns must be projected in time division in the space coding method, a high-speed data inputting operation is difficult. Similarly, in the triangulation method using a laser light, because only one laser beam can be irradiated and this one laser beam must be scanned, there is a problem that a high-speed data inputting operation is difficult.